This invention relates to a method for the asymmetric hydrogenation of .alpha.-ketoesters in the presence of a specific catalyst.
A variety of studies have been made heretofore on the methods for the asymmetric hydrogenation of .alpha.-ketoesters. For example, there are known a method wherein a benzoylformate or a pyruvate is reacted with hydrosilane in the presence of a rhodium complex containing an optically active ligand and then the reaction product is decomposed and a method wherein an optically active 1,4-dihydronicotinamide derivative as the so-called NADH model compound, i.e. a typical coenzyme of an enzyme for biochemical reduction reactions, is reacted in the presence of magnesium perchlorate with methyl benzoylformate to obtain an optically active mandelate in an extremely high yield of the asymmetric product.
However, the methods for the asymmetric hydrogenation of .alpha.-ketoesters proposed heretofore have such drawbacks that a catalyst used therein is liquid and is thus difficult to separate itself from the reaction product and that the preparation of such catalyst is difficult. If it is possible to use a solid catalyst for these methods, the above described drawbacks will be overcome. However, a solid catalyst exhibiting a high rate of asymmetric hydrogenation has not yet been developed.